The process described herein is applicable to the conversion of petroleum crude oil residuals having a high metals content and comprising a hydrocarbon-insoluble asphaltene fraction. More specifically, our invention is directed toward a method for effecting a catalytic slurry process, in the presence of hydrogen, in order to convert atmospheric tower bottoms, vacuum column bottoms, crude oil residuals, topped and/or reduced crude oils, coal oil extracts, crude oils extracted from tar sands, shale oil, etc., all of which are commonly referred to in the art as "black oil".
Petroleum crude oils, and particularly the heavy residuals derived therefrom, contain sulfurous compounds in exceedingly large quantites, nitrogenous compounds, high molecular weight organometallic complexes principlally comprising nickel and vanadium as the metallic component and hydrocarbon-insoluble asphaltenic material. The latter is generally found to be complexed with sulfur, and, to a certain extent, with the metallic contaminants. A black oil is generally characterized in petroleum technology as a heavy hydrocarbonaceous material of which more than about 10.0 percent (by volume) boils above a temperature of about 1050.degree. F. (referred to as nondistillables) and which further has a gravity generally less than 20.0 .degree.API. Sulfur concentrations are exceedingly high, most often in the range of about 2.0 to about 6.0 percent by weight. Canradson carbon residual factors exceed 1.0 percent by weight and the concentration of metals can range from as low as about 20 ppm to as high as about 2000 ppm by weight.
The process encompassed by the present invention is particularly directed toward the conversion of those black oils contaminated by large quantities of insoluble asphaltenes and having a high metals content, i.e. containing more than about 150 ppm by weight. Specific examples of the charge stocks to which our invention is adaptable include a vacuum tower bottoms product having a gravity of 7.1 .degree.API and containing 4.1 percent by weight of sulfur and 23.7 percent by weight of heptane-insoluble materials; a "topped" Middle-East crude oil having a gravity of 11.0 .degree.API and containing about 10.1 percent by weight of asphaltenes and 5.2 percent by weight of sulfur; and, a vacuum residuum having a gravity of 8.8 .degree.API, containing 3.0 percent by weight of sulfur and 4300 ppm by weight of nitrogen.
Candor compels recognition of the fact that many slurry-type processes have been proposed. Regardless of the various operating and processing techniques, the principal difficulty resides in the separation of the effluent to provide substantially catalyst-free distillable product, uninterrupted catalyst recirculation and continuous, smooth, unimpeded flow of the reactants and the slurry catalyst through the entire process and particularly in the reaction zone.
The black oil is typically utilized in a slurry catalyst process and is inherently susceptible to the formation of coke when exposed to hydrocarbon conversion temperatures. Our invention affords an improved catalytic slurry process for black oil conversion by reducing the formation of undesirable coke and any other undesirable deposits and thereby improving process stability.